This invention relates to the construction of bridges, roadways, parking garages, pedestrian walkways, and similar structures and more particularly to expansion joints disposed between the slabs or other elements that form these structures. The need for such expansion joints between adjacent structural members to permit movements caused by changes in the ambient temperature has long been recognized within the art. In reality, there are actually many kinds of relative movement between adjacent structural members and all of these movements must be considered in the design of a successful expansion joint. For example, up and down movements caused by traffic loadings can occur. Relative rotation of the structural members can also occur. Growth of the joint opening, caused by shrinkage of concrete pavement sections, may also occur in addition to the continual effects of thermal expansion and contraction.
The prior art includes various structures which are generally relevant. U.S. Pat. No. 4,290,249 to Mass describes an elastomeric spring expansion joint-seal strip that is generally M-shaped. The structure described therein appears to rely exclusively on its compressive characteristics to achieve its sealing abilities. Many factors, such as irregularities in the joint sides, and especially excessive width of the joint opening, make this and other compressive seal designs unlikely to be fully watertight. This design also requires spring means embedded within the seal strip. These spring means increase the fabrication costs of this seal strip. U.S. Pat. No. 4,295,311 to Dahlberg describes an expansion joint element for forming a surface joint between two concrete construction parts. The structure described therein is difficult to install in many cases because the traffic cannot run over this structure until sufficient time has elapsed for its adhesive bonding material to cure. This cure period is often too long to accommodate modern traffic conditions. Moreover, this expansion joint is often installed in individual sections which must be joined together at the time of installation. These "stage joints" are notoriously prone to failure and leakage.
U.S. Pat. No. 4,111,584 to Fyfe describes an inverted U-shaped member that is clamped to the opposed walls and which is further restrained by complex abutments. The nature of the abutment ensures that the structure would be difficult and time consuming to install as well as expensive to manufacture. Other prior art patents actually require the installation of a portion of the seal to be embedded in the slabs of the bridge or other structure. See for example U.S. Pat. No. 3,172,237 to Bradley and the known Wabocrete/Membrane 101 System.
Although these types of seals bear some resemblance to the present invention because they have side flaps, there is in fact a very important difference between them and the present invention. Namely, the side flaps of such seals are "buried" underneath the joint header material which makes their removal and replacement for maintenance purposes very expensive. This is because all of the header material must be removed and then replaced in order to install a new one of these seals. In the present invention the seal apparatus may be removed and replaced without concurrent removal of the joint headers. Another, general problem with designs of this type is that water collects in the "V's" between the headers and the sealing element and this water can migrate under the headers and expand when it freezes. This can lead to break up of the joint headers. In the present invention, the water collects only in the elastomeric portions of the sealing element where freezing water can do no damage.
Other U.S. Pat. Nos. of background interest include 3,381,436; 3,829,228; 3,838,931; 3,850,539; 4,285,612; and 4,634,133.
It is imperative that the expansion joint prevent the harmful passage of water through the joint opening. This is particularly harmful in bridges because the water can cause very severe damage to the bridge bearing devices that accommodate expansion and contraction of the bridge sections. Damage to the steel superstructure can also be caused by the water which also results in frequent maintenance procedures.
Many known seals for such joints incorporate metal plates, angles, extruded "jaws" and the like. Such materials are referred to herein as "metal work". Along with other drawbacks, metal work is difficult to repair should it become damaged.
Another problem with the prior art apparatus is that it often will not function when the interface between concrete sections has steps or bends. Stated another way, the prior art seals often do not satisfactorily cooperate with sharp upturns, downturns, or sideways bends in the joint opening. Such angular bends of the joint opening are often encountered at curbs, on bridges and other structures.
Still other problems with the known seals is that they do not consistently prevent the accumulation of excessive foreign matter, such as sand and gravel, in the joint. Another problem with many known seals is that the seal has a relatively large height and this limits the places where the seal can be installed and particularly may prevent installation on many bridges that are being repaired. Many known seals will not function when there is a variation in the width of the joint opening along the longitudinal extent thereof. Because there are inherently substantial tolerances in the placement of the huge slabs and the like involved in such structures it is undesirable to have a seal that will not function in such an environment.
It is an object of the invention to provide a seal apparatus that is capable of accommodating a wide variety of different movements.
It is another object of the invention to provide a seal that will prevent the passage of water into the space between concrete or other slab shaped sections of material.
It is another object of the invention to provide a seal that can be replaced without concurrent removal of the joint headers.
Still another object of the invention is to provide a seal that has a relatively low height and thus will be dimensionally suitable for installation in a wide range of applications.
Yet another object of the invention is to provide a structure that can easily accommodate itself to different roadway cross slopes, as well as to width variation (or "waviness") of the joint opening.